MySQL with Orchestrator and ProxySQL seems to get out of sync

[Bart Bania]

This is weird.

You introduced ProxySQL + orchestrator into the setup, yet, the wordpress connects via hosts file entry to one MySQL server only, leaving out orchestrator...

from wp-config.php on both nginx nodes:

/** MySQL hostname */
define( 'DB_HOST', 'DB_1' );

From /etc/hosts file on both nginx nodes:

bash-4.2# cat /etc/hosts
x.x.x.x DB_1 db_1
y.y.y.y DB_2 db_2

This poses several issues:

1. unnecessary cost coming out of the fact, there's additional, not used node.
2. problems with writing into the database - both nginx services want to write to one, and this can cause problems with writes, breaking replication.

You should either:

1. make sure Wordpress connects through proxysql, not directly to 1 node
2. get rid of orchestrator and set up the database connection in a more proper way, e.g. using haproxy or proxysql installed on nginx nodes?

[Bart Bania]

I believe this may be related to previous, similar request: #2

Our customers experienced similar issues with being thrown out of wordpress admin.

We've noticed MySQL was constantly going out of sync and replication being broken all the time.

[Henadii Sychevskyi]

Hello! Thank you for the notes.
Proxysql node shouldn't be avail in the topology. It is added by mysql autoclustering when creating the topology, with 2 or more nodes mysql in the layer. Also, autoclustering configured master-slave replication by default, contrary to master-master, which is used by cluster. I disabled autoclustering from the topology while creation of wordpress-cluster.

Connect with DB is implemented via HyperDB plugin, where DB_1 and DB_2 are described.
https://github.com/jelastic-jps/wordpress-cluster/blob/master/configs/wordpress/db-config.php#L217
https://github.com/jelastic-jps/wordpress-cluster/blob/master/configs/wordpress/db-config.php#L228
When one of the sql-nodes is down, cluster will be up and running.
Proxysql is being tested at the moment.

Thanks,

[Bart Bania]

Hmm... that is weird, as wp-config has

/** MySQL hostname */
define( 'DB_HOST', 'DB_1' );

at least on our installations, how is that file (db-config.php) overriding wp-config?

And still, somehow wordpress tends to break replication with primary key violations on data import...

[Bart Bania]

Hi,

To be honest, I believe that what you're missing is MySQL config parameters:

auto_increment_increment
auto_increment_offset

Those should make autoincrement work sanely with master-master.

[Henadii Sychevskyi]

The configuration must be present in the my.cnf file after wp-cluster is deployed.

Could you please deploy the cluster and check my.cnf conf file ?